To respond to the growing needs of flow rates in the transmission of information, Wavelength-division Multiplexing systems (WDM) are used. WDM consists in combining a plurality of signals at different wavelengths in a single optical fiber. According to this method, the global flow rate of the optical fiber is the sum of the flows rates of all the signals. However, the wavelength of each signal must be controlled precisely, in emission and in reception, to avoid signal interferences.
An uncontrolled wavelength of the emission of a signal may cause said signal to flow at the same wavelength as another signal in the same optical fiber, causing the quality of both signals to decline. Such interference is also called a spectral collision. The reception of an uncontrolled signal by a receiver device may also cause a degradation of the quality of both signals or even the detection of another signal than the one which was intended to said receiver device. To control the wavelength of each signal transmitted by an optical fiber, optical emitter devices having a tunable wavelength can be used in WDM.